Nanoencapsulated phase change materials with polymer-SiO2 hybrid shell materials: Compositions, morphologies, and properties

Abstract

Organic-inorganic hybrid materials are promising for encapsulation of phase change materials (PCMs) to achieve exceptional capsule properties. In this work, novel polymer-SiO2 hybrid shelled nanoencapsulated PCMs (NanoPCMs) were fabricated in one-pot, through sequentially executed interfacial hydrolysis-polycondensation of alkoxy silanes and radical polymerization of vinyl monomers. The morphologies, chemical compositions, and crystal structures of the NanoPCMs were characterized by SEM, TEM, FT-IR, and XRD methods. The thermal energy storage capability, thermal reliability, and thermal conductivity were tested by DSC, accelerated thermal cycling test, and heat flux method, respectively. The leakage proof property and mechanical property were evaluated by seepage test and nanoindentation test, respectively. Compared with NanoPCMs with SiO2 shell, the NanoPCMs with polystyrene (PS)-SiO2 shell possess smaller size and bowl like shape, while NanoPCMs with poly(hydroxylethyl methacrylate) (PHEMA)-SiO2 shell possess larger size and perfect spherical shape. The polymer types have great impact on the supercooling behavior of the NanoPCMs. The polymer-SiO2 hybrid shell materials endow the NanoPCMs with improved thermal reliability, thermal conductivity, and leakage proof property. More importantly, the compressive load at yield increases remarkably from 14.7 μN for nanocapsules with SiO2 shell, to >34.6 μN for that with PS-SiO2 shell, and 65 μN for that with PHEMA-SiO2 shell.